Aristiana,
 
It took me about two months and a lot of patience to get my older ferret
to play nicely with my two newer ferrets, but now they are the best of
friends.  One trick that seemed to work was to keep two of them (the
older one and one of the young ones) together in a small space while I
supervised.  Often, I would put a bunch of cozy blankets in the bathtub
and sit in there with them trying to get them to fall asleep near each
other.  I tried to make it a safe space, so if one of them looked about
to threaten the other, I would gently circle him around the neck to keep
him at a safe distance.
 
Best of luck,
Julie
[Posted in FML issue 3329]